Seety have beat Google somewhat to the table with a pretty comprehensive coverage of central London using street based panoramic imagery.
Navigation is nice, although not quite as smooth as Googles own street view product, the main question we have to ask is why? Its well known that Google is currently driving the streets of Europe capturing imagery and with it bound to be a default layer in a few months you have to ask why anyone else would do it?
London UK street level views, but not from Google from Brian Norman on Vimeo.
Licencing and use of imagery maybe a factor - Seety is being used by Earthware (a company worth watching) in the the latest version of our Earthware Property real estate mapping solution. The movie above demonstrates Seety imagery within the Earthware interface.
However with open use of the Google API we assume that property searches will make copious use of street view as soon as its available and where does that leave Seety (?)
Lots of questions we know...
See http://www.earthware.co.uk/ and http://www.seety.co.uk/ for more info and demos.